Zinc Anode in a Salt Pool to prevent heater erosion?

[dfiletti]

Folks-

Just dropped by a local pool store, to pickup CYA. It was not my normal pool store, but it was on the way. So I get chatting with the shop owner and he starts talking about how salt pools are now being implicated in heater erosion issues. He says he's just started installing Zinc Anodes in the pump system somewhere to reduce the erosion associated with the salt. Further, he said it would cost me a mere $200.00 to have such a thing installed, including wiring it to the box, on my pool. I do know that my boat motor has a sacrificial anode on it, for use in salt water, and that it's purpose is to prevent erosion of the metal on the motor.

I'd appreciate any input any of you had as to whether this would be good/ bad for the water (as I'm nearly certain that the design principles of the boat anode were not focusing on water quality). Also, does it need to be wired to the electric box? Are they a good idea/ bad idea, not worth it? can the same thing be done by just dropping a hunk of zinc in a skimmer basket?

As always, input is greatly appreciated.

Thanks,

Dan

 

[JasonLion]

An anode gets wired to the bonding system and buried in the ground. They don't seem to make much difference. Maintaining proper PH levels is far more important for the life of the heater than the difference having an anode makes.

 

[chem geek]

It would need to be wired electrically to the same bonding wire connected to the copper heat exchanger in the gas heater. You should also make sure there is no aluminum connected to that same bonding wire (if there is, then the sacrificial anode should be magnesium, not zinc [EDIT] actually, zinc is OK to protect aluminum as well based on the galvanic series, not just the standard reduction potential [END-EDIT] ). It won't cause harm, but it may not be needed. The higher salt level is more conductive and corrosive, but as to whether it will affect your heater depends on many factors including typical pool pH. If the heater uses titanium or cupro-nickel alloy materials, then there is no need for the extra protection for the heater. The plus for using an anode is that it will also help protect everything else connected to the bonding wire including stainless steel.

Usually, the problems we've seen in higher salt level pools have been with those pools not using CYA and at higher chlorine levels, but that was pretty extreme corrosion of stainless steel in less than a year. We've also seen problems on aluminum tracks/rails for automatic pool covers from salt water splash-out.

This seems pretty pricey for a block of zinc so I suspect most of the cost is the labor and this sounds like something you could probably do yourself if you wanted to. The sacrificial anode is often buried in moist soil.

Do note that most people with SWG pools do not use sacrificial anodes and most do not report corrosion problems. It's a matter of increased risk so if you were on the edge (for other reasons) then it might be worth it; otherwise, it wouldn't hurt but might not help in a noticeable way.